750s/255 wierd results.

[eclipse90gsxt]

Ok I own a 90 GSX and bought 750's, 255(non rewired), and am getting wierd results.

My mods are in my profile, basically a Big16G ported untill I buy my GT-12. Now with a 255 and 750's my friend who I bought the parts from ran -40% across the low and -10 high. He ran a 60-1, so high is going to be different of course.

Anyways, My car with about 115% high,mid,low fuel trims are only at -28%, which seems wierd to me since I thought I would be taking out a lot more fuel.

At WOT I would think I would have to take out more than 10% because my friends 60-1 flows a lot more air than my Big16G. I take out 5% and get .86-.75 02's, and 10-20 counts of knock. I have the stock Mas and stock fpr. I am going to buy a AFPR tommarrow and a gauge, but I am confused by my numbers.

The only X factor I have is that I only have 12hg at idle, which I know itsn't helping. Is my vaccum leak making these numbers? I the fuel rail is from a 2G I believe and so is the FPR, which I just bought the injectors from him with the rail/pump for cheap.

Any help is greatly appreciated.

 

[talon1979]

Boost and vacuum leaks will definately mess up your low fuel trim. If your car is at 28% on your low fuel trim that means that the car is seeing WAY to much fuel at idle. You will need to lean your car WAAYYY out for you low fuel trim to shoot back up. I would recommend going to www.dsmchips.com and getting a chip that will compensate for your injectors. If you throw in race fuel you may be so lean on your SAFC that you will get too much timing advance.

 

[kpt4321]

Originally posted by eclipse90gsxt
My mods are in my profile, basically a Big16G ported untill I buy my GT-12. Now with a 255 and 750's my friend who I bought the parts from ran -40% across the low and -10 high. He ran a 60-1, so high is going to be different of course.

A couple of things:

First of all, your friend is now banned from tuning your car. -10% on the hi throttle map with 750's is absolutely absurd. You could go to -25% and still be VERY VERY conservative.

Second of all, SAFC corrections are not very dependant on the turbo being used. They are much more effected by the other parts of the car like the fuel system and the intercooler.

Anyways, My car with about 115% high,mid,low fuel trims are only at -28%, which seems wierd to me since I thought I would be taking out a lot more fuel.

Do you mean that all three of your fuel trims are 115%? If that is true, then you need to richen the car up in that range on the SAFC.

At WOT I would think I would have to take out more than 10% because my friends 60-1 flows a lot more air than my Big16G. I take out 5% and get .86-.75 02's, and 10-20 counts of knock. I have the stock Mas and stock fpr. I am going to buy a AFPR tommarrow and a gauge, but I am confused by my numbers.

Something is wrong here. You should be able to lean the car out quite a bit, like -30% or more. The fact that you have not gone that far makes me wonder if the injectors are really as big as you think, or if something else is wrong.

The only X factor I have is that I only have 12hg at idle, which I know itsn't helping. Is my vaccum leak making these numbers? I the fuel rail is from a 2G I believe and so is the FPR, which I just bought the injectors from him with the rail/pump for cheap.

Yes. A bigass vacuum leak will make tuning VERY difficult.

 

[eclipse90gsxt]

Well a to make a few things clear, I am running I think a 2G fuel Rail with a 2G fpr and to make the 02 cycle right I am currently -28% on the low map, and -5% on the high map. I know they are indeed 750's, and the 255 is hooked up right, so that was what making me confused.

I believe the rail is a 2G, but I know the 10hg at idle (750-800) isn't helping.

I am running 20lbs, and at -5% on the high I am getting .86-.84 02 volts and a few counts of knock, which also confused me.

 

[Violater101]

A vacuum leak will cause havoc on tuning. Get that fixed, then try to adjust the AFC. There is no point in even trying until you get that fixed imo.

 

[eclipse90gsxt]

THats what I figured, I just haven't had the time or will, since it is like 20 degrees out side. Upstate NY sucks. I will fix it tommarrow and see what happens.